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                  <p class="p_Heading1"><span class="f_Heading1">Sequence Diagram</span></p>



  
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                <p class="p_BodyText"><span class="f_BodyText">A </span><span class="f_BodyText" style="font-style: italic;">Sequence</span><span class="f_BodyText"> diagram is one of four types of </span><span class="f_BodyText" style="font-style: italic;">Interaction</span><span class="f_BodyText"> diagram. (The other three are <a href="timingdiagram.htm">Timing Diagram</a>, <a href="interactionoverviewdiagram.htm">Interaction Overview Diagram</a> and <a href="communicationdiagram.htm">Communication Diagram</a>.)</span></p>
<p class="p_BodyText"><span class="f_BodyText">A </span><span class="f_BodyText">Sequence</span><span class="f_BodyText"> diagram is a structured representation of behavior as a series of sequential steps over time. It is used to depict work flow, message passing and how elements in general cooperate over time to achieve a result.</span></p>
<ul style="text-indent: 0px; margin-left: 30px; list-style-position: outside;">
<li><span class="f_Bulletlist1">Each <a href="sequenceelements.htm">sequence element</a> is arranged in a horizontal sequence, with messages passing back and forward between elements.</span></li>
<li><span class="f_Bulletlist1">An Actor element can be used to represent the user initiating the flow of events.</span></li>
<li><span class="f_Bulletlist1">Stereotyped elements, such as <a href="boundary.htm">Boundary</a>, <a href="control.htm">Control</a> and <a href="entity.htm">Entity</a>, can be used to illustrate screens, controllers and database items, respectively.</span></li>
<li><span class="f_Bulletlist1">Each element has a dashed stem called a lifeline, where that element exists and potentially takes part in the interactions.</span></li>
</ul>
<p class="p_BodyText"><span class="f_BodyText">To configure a Sequence diagram, see the following topics:</span></p>
<ul style="text-indent: 0px; margin-left: 30px; list-style-position: outside;">
<li><span class="f_Bulletlist1"><a href="denotelifecycleofanelement.htm">Denote the Lifecycle of an Element</a></span></li>
<li><span class="f_Bulletlist1"><a href="layoutofsequencediagrams.htm">Layout of Sequence Diagrams</a></span></li>
<li><span class="f_Bulletlist1"><a href="sequenceelementactivation.htm">Sequence Element Activation</a></span></li>
<li><span class="f_Bulletlist1"><a href="lifelineself_messagehierarch.htm">Lifeline Activation Levels</a></span></li>
<li><span class="f_Bulletlist1"><a href="sequencemessagelabel.htm">Message Label Visibility</a></span></li>
<li><span class="f_Bulletlist1"><a href="changing_the_top_margin.htm">Change the Top Margin</a></span></li>
<li><span class="f_Bulletlist1"><a href="changing_the_timing_details.htm">Change the Timing Details</a>.</span></li>
</ul>
<p class="p_BodyText"><span class="f_BodyText">Also take note of the important information in the </span><span class="f_BodyText" style="font-style: italic;"><a href="sequence_diagrams_and_version_.htm">Sequence Diagrams and Version Control</a></span><span class="f_BodyText"> topic.</span></p>
<p class="p_BodyText"><span class="f_BodyText" style="font-style: italic;">Robustness diagrams</span><span class="f_BodyText">, used extensively in </span><span class="f_BodyText" style="font-style: italic;"><a href="iconix_process.htm">ICONIX</a>, </span><span class="f_BodyText">can be created as Sequence diagrams.</span></p>
<p class="p_BodyText"><span class="f_BodyText">To toggle the numbering of messages on a Sequence diagram, select or deselect the </span><span class="f_MenuKeyField"><a href="sequencediagrams.htm">Show Sequence Numbering</a></span><span class="f_BodyText"> checkbox on the </span><span class="f_UIControl">Options</span><span class="f_BodyText"> dialog</span><span class="f_BodyText" style="font-style: italic;">.</span></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">Example Diagram</span></p>
<p class="p_BodyText"><span class="f_BodyText">The following example Sequence diagram demonstrates several different elements:</span></p>
<p class="p_TextIndentedL2"><img src="example%20of%20a%20sequence%20diagram.png" width="676" height="603" border="0" alt="Example of a Sequence Diagram"></p>
<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">Toolbox Elements and Connectors</span></p>
<p class="p_BodyText"><span class="f_BodyText">Select Sequence diagram elements and connectors from the </span><span class="f_UIControl"><a href="interactiongroup.htm">Interaction</a></span><span class="f_BodyText"><a href="interactiongroup.htm"> pages</a> of the Enterprise Architect UML</span><span class="f_UIControl"> Toolbox</span><span class="f_BodyText" style="font-style: italic;">.</span></p>
<p class="p_BodyText"><span class="f_BodyText">Enterprise Architect also supports a number of <a href="business_interaction.htm">stereotyped elements</a> to represent various entities in business modeling.</span></p>
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<td valign="bottom" width="955" bgcolor="#efeff7" style="width:955px; background-color:#efeff7;"><p class="p_TiporNote" style="border-top: none; border-right: none; border-left: none;"><span class="f_TiporNote">Tip:</span></p>
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<td width="955" bgcolor="#f7f7ff" style="width:955px; background-color:#f7f7ff;"><p class="p_TiporNoteText"><span class="f_TiporNoteText">Click on the following elements and connectors for more information.</span></p>
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<td valign="top" width="205" bgcolor="#e3e6ed" style="width:205px; background-color:#e3e6ed; border: solid 1px #000000;"><p class="p_Tableheader"><span class="f_Tableheader">Sequence Diagram Elements</span></p>
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<td valign="top" width="204" bgcolor="#e3e6ed" style="width:204px; background-color:#e3e6ed; border: solid 1px #000000;"><p class="p_Tableheader"><span class="f_Tableheader">Sequence Diagram Connectors</span></p>
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<p class="p_SubHeadingL1"><span class="f_SubHeadingL1">OMG UML Specification</span></p>
<p class="p_BodyText"><span class="f_BodyText">The OMG UML specification (</span><span class="f_BodyText" style="font-style: italic;">UML Superstructure Specification, v2.1.1, p. 503</span><span class="f_BodyText">) states:</span></p>
<p class="p_OMGText"><span class="f_OMGText">A sequence diagram describes an Interaction by focusing on the sequence of Messages that are exchanged, along with their corresponding OccurrenceSpecifications on the Lifelines.</span></p>




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